Optoelectronic semiconductor chips can include a component layer sequence, including active (photon generating) layers, grown epitaxially on a substrate. The substrate onto which the active (photon generating) layers are grown epitaxially has an important influence on the quality of the active layers. If the substrate exhibits defects, defects are likely to be formed in the active layers epitaxially grown on this substrate as well. Furthermore, if the lattice constant of the substrate is different from the lattice constant of the epitaxially grown layers, strain can be induced in the active layers. Consequently the quality of the substrate influences the active layers.
Particularly in the case of optoelectronic semiconductor chips based on compound semiconductor materials that are grown epitaxially on substrates which do not originate from the same material system (where this term refers to a plurality of materials based on the same group-V element, e.g. As, N, P) as that of the component layer sequence, there is a need to reduce the influence of the substrate quality on the active layers of the component layer sequence. This is of importance in particular for semiconductor laser diode chips, and especially for those with an InGaAIP-based laser diode structure, which is frequently grown on GaAs substrates. However, a similar situation also applies, for example, to other optoelectronic semiconductor chips based on InGaAlP.
The group of optoelectronic, viz. radiation-emitting and/or radiation-detecting, semiconductor chips based on InGaAlP includes in particular those chips in which the epitaxially fabricated radiation-generating semiconductor component layer sequence, which generally has a layer sequence made of various individual layers, contains at least one individual layer which has a material from the III-V compound semiconductor material system InxAlyGa1-x-yP where 0≦x≦1, 0≦y≦1 and x+y≦1. The semiconductor component layer sequence may have, for example, a conventional pn junction, a double heterostructure, a single quantum well structure (SQW structure) or a multiple quantum well structure (MQW structure). Such structures are known to the person skilled in the art and, therefore, are not explained in any further detail herein.